Quantifying Ligand Binding to the Surface of Metal-Organic Frameworks

The binding of molecules to the exterior surface of metal-organicframeworks (MOFs) is not a well-understood phenomenon. Herein, thesurface chemistry of three MOFs, UiO-66, MIL-88B-NH2, andZIF-8, is investigated using dye-displacement experiments. MOF particlesurfaces were modified with ligand-appended BODIPY dyes. The abilityof the coordinated dyes to be displaced by a variety of exogenousligands was measured by ultraviolet-visible spectroscopy. This methodallowed for measurement of apparent binding constants for differentligands to the MOF surface. As might be expected, ligand affinitywas dependent on the nature of the underlying metal-ligandcomposition of the MOF. This work provides a quantitative evaluationof ligand binding to MOF surfaces and important insights for the modulation,modification, and manipulation of MOFs.